ISO/IEC 13818-1 is an international standard that specifies the coding of one or more elementary streams of audio and video as well as other data into single or multiple streams suitable for storage and transmission. Two forms of coding are recommended: Program Stream (PS) coding and Transport Stream (TS) coding. In the coding process, Audio-Visual (A/V) streams are first compressed and packetized to obtain Packetized Elementary Streams (PES). The PS combines one or more streams of PES packets with a common time base into a single stream. The TS combines one or more programs with one or more independent time bases into a single stream. PS packets may be of variable length, and TS packets are 188 bytes in length. Each TS packet has a 4-byte header with a packet ID (PID) that identifies the type of data contained in the packet. In addition to PES packets, a TS contains Program Specific Information (PSI) tables to demultiplex and present programs. A Program Map Table (PMT) is a table that provides the mappings between the program numbers and the elements that comprise them. It includes a list of PIDs associated with each program.
The Advanced Television Systems Committee (ATSC) has adopted the Simulcrypt architecture for its Conditional Access (CA) system for terrestrial broadcast. In this architecture, each service is transmitted with Entitlement Management Messages (EMMs) and Entitlement Control Messages (ECMs) for a number of different proprietary systems. This way, decoders using different CA systems can decode the service using a common framework for signaling the different entitlement messages. Each service is comprised of audio and video packets. Any one decoder picks out the packets it needs and ignores the others in the stream.
In a Simulcrypt based CA system, a digital audio/video processing system, such as a Digital Television (DTV) parses the PMT and extracts the service and ECM PIDs using a CA system identification (ID) obtained from the CA module. Normally, each CA module supports only one CA system, and therefore has only one CA system ID. The PIDs of the A/V packets and the PIDs of the ECMs carrying the Control Words (CWs) are sent to the CA module, which descrambles programs having proper purchase entitlements.
U.S. Pat. No. 5,420,866 to Wasilewski describes a method for providing conditional access information to a plurality of different decoders which is very similar to a Simulcrypt system. Wasilewski describes using a CA system identification parameter CA_System_ID to identify the different CA providers, and hence the different decoders (see col. 12, lines 12-16).
Additionally, an article entitled “Wunderkiste des digitalen Fernsehens” by Daniel Kramer mentions the Simulcrypt technique (Kramer D: “Wunderkiste des digitalen Fernsehens”, Bull. SEV/VSE, CH, Schweizerischer Elektrotechnischer Verein, Zurich, Vol. 88, No. 3, pp. 27-30).